Tumor necrosis factor alpha and interleukin-6 have differential effects onfood intake and gastric emptying in fasted rats

Interleukin-1 (IL-1), IL-6, and tumor necrosis factor (TNF) are thought to mediate the onset of anorexia with infection. Animal studies suggest that g astric stasis accompanies IL-1-induced anorexia, and that food intake and g astric emptying of IL-1-injected rats are improved by pretreatment with ibu profen (ibu), an inhibitor of prostaglandin (PG) synthesis. The purpose of the present study was to determine if gastric stasis accompanies the reduce d food intake induced by intraperitoneal injection of TNF alpha or IL-6 and whether these effects are mediated by PG. Injection of TNF alpha reduced f ood intake of fasted rats, but did not affect gastric emptying; injection o f IL-6 reduced both food intake and gastric emptying. Pretreatment with 1.0 mg/kg ibu improved food intake of TNF alpha-injected animals, but did not affect food intake or gastric emptying of IL-6-injected animals. These data indicate that although IL-6 and TNF alpha have overlapping effects on food intake, the mechanisms of action are not identical. Delayed gastric emptyi ng does not play a major role in the anorexigenic effects of TNF alpha, and PG synthesis does not play a major role in the anorexigenic effects of IL- 6. These findings may be helpful in the development of interventions to imp rove nutritional intake during infection. (C) John Wiley & Sons, Inc.